This invention relates to electric fuel pumps for use in automotive vehicles; and more particularly, to an improved construction for mounting an impeller to a drive shaft by which an electric motor driving the pump causes the impeller assembly of the pump to rotate, the improved construction reducing shaft wear and improving service life of the pump.
A high-pressure electric fuel pump such as is commonly used in fuel injected automobile engines includes a housing in which is encased an electric motor and an impeller assembly driven by the motor. The impeller assembly is mounted on a drive shaft driven by the motor, with the suction created drawing low-pressure fuel into the pump from a fuel tank or reservoir of a fuel module. The impeller is designed to increase the fuel pressure from approximately atmospheric pressure on the input side of the pump to pressures ranging to 50 psi and higher on the outlet side of the pump, depending upon the particular application.
Heretofore, the drive shaft has generally been a round shaft such as shown in FIG. 1A, although other shaped shafts have been used. U.S. Pat. No. 4,209,284, for example, describes a drive shaft, referred to as a D-shaft (see prior art FIG. 1B), because a portion of the shaft is flattened so that the contour of the shaft, viewed axially, resembles the letter D. In U.S. Pat. Nos. 5,722,815 and 5,711,408 opposite portions of the shaft are flattened to create what is referred to as a “double-D” contour. There are also shaft constructions in which an intermediate or end portion of an otherwise circular shaft is shaped into an X pattern such as shown in U.S. Pat. No. 4,978,282, or a square shape with rounded corners such as shown in U.S. Pat. No. 4,639,202. These latter profiles are for mounting and locking the impeller assembly onto the shaft to improve pump efficiency by reducing the effects of wear between the impeller and motor shaft.
While the various constructions shown in these patents may work for their intended purpose, there are improved impeller constructions by which the impeller assembly is mounted on the shaft and which are less susceptible to wear and further increase the efficiency of the fuel pump.